OAKLAND -- One man was detained and two others were being sought on suspicion of shooting a police officer in the arm Monday night, police Chief Howard Jordan said.

Jordan said the officer -- an undercover detective -- was sitting in a car in the 1700 block of Seminary Avenue when he was shot about 6:22 p.m. The officer was in the neighborhood investigating a shooting in the 5900 block of Foothill Boulevard on Sunday that left a man with life-threatening injuries, police said. The officer, who was not identified, was taken to a hospital for treatment and is expected to recover.

The shooting sparked a massive hunt in the East Oakland neighborhood, where SWAT officers and a California Highway Patrol helicopter were called in to assist with the search.

Police set up a perimeter near the 1700 block of Seminary Avenue after an undercover detective was shot in the arm while investigating a previous shooting. (Erin Ivie/Staff)

One unidentified man was detained later Monday, Jordan said, and officers were still seeking two others in connection with the incident.

Jordan would not say if the suspects were in a car or on foot at the time of the shooting, but police earlier said that one of the suspects was seen holding a gun as he ran from the scene. A second weapon was also recovered at the shooting scene, but it wasn't immediately known which weapon was used to shoot the officer.